Do all agents require you to get pre-qualified/pre-approved befor

[Tom Smith]

I have never purchased a home before and am renting right now.

Do all agents require you to get pre-qualified/pre-approved before actually showing you homes? What percentage of agents will require that you get pre-qualified and pre-approved before showing you homes in the area? Also, should you use their lenders or find your own? What are the pros and cons of each? 

Thank you.